The invention relates to clamping or expanding pliers having two pliers arms which are connected to one another in the manner of a scissors articulation and form, at one end, handle sections and, at the other end, clamping sections which can be moved toward one another when the handles are actuated, it being possible for the two pliers arms to be latched in clamping positions with the clamping sections in a diversity of spaced apart positions.
From the Gxc3x6dde catalog 1989, page 531, there is known clamping pliers for installation or assembly purposes, as also find use in the field of surgery. The clamping force is based on the restorable deformability of the pliers legs. The blades are thus of relatively narrow configuration, as are likewise the relatively long pliers jaws. In practice, they are similar to tweezers arms. The respective clamping position can be fixed by a releasable locking clamp. Corresponding tooth-like latching protrusions are located between the blades. The release operation requires the pliers arms to be twisted. This may result in the pliers jaws being offset in relation to one another.
Also known are stamped formations on cable cutters and pruning shears (U.S. Pat. No. 1,454,917, U.S. Pat. No. 4,062,218, GB patent specification 1 056 176) by way of which a toothed segment and a disengageable catch are disposed such that the pliers arms remain free from twisting. These solutions, however, require high-outlay gear mechanisms.
It is an object of the invention for clamping pliers of the generic type to be kept free of twisting forces in the knuckle joint, but nevertheless to be configured more straightforwardly in structural terms.
This object is achieved first and foremost, in the case of clamping pliers having the features of claim 1, by an arcuate toothed strip which is associated with one pliers arm and in the toothing formation of which there engages a catch which is associated with the handle section of the other pliers arm. The arcuate toothed strip may be integrated, which reduces the number of parts. The catch is associated straightforwardly with the other pliers arm. This can take place in the spatial vicinity of the knuckle joint, so that the release can also be controlled very well in terms of ergonomics. Should the clamping pliers consist of plastics material, then, for the purposes of maximizing the wear strength, the arcuate toothed strip may consist of a relatively harder plastics material than the pliers arms themselves. The arcuate toothed strip is in advantageous manner positioned in a recess of a pliers arm. In structural terms, this is such that the arcuate toothed strip is pinned to the pliers arm by means of the scissors-articulation pin and is supported thereon. It is further proposed for the clamping sections of the pliers arms to carry tiltable clamping jaws at the ends. This makes it possible, in each expanded position, for a plate-like object to be gripped in a plane-parallel manner on both sides. A further contribution of the invention is that the one pliers arm provides an opening through which the other pliers arm is inserted, this achieving the so-called inserted type of articulation for the tool. This solution is further characterized in that the inwardly-located, that is to say through-engaging pliers arm, carries the arcuate toothed strip. The solution proves favorable in terms of actuation in that the catch forms an actuating section which projects into the handle section. The actuating section is in advantageous manner located in a window of the handle section. The arrangement by which the handle section has a U-shaped cross-section, in the cavity of which the catch is rotatably located, proves favorable in structural terms and has a material-saving effect. The handle section itself has a bearing pin which passes through the cavity and is intended for the catch. It is advantageous then that the pliers arms are mounted resiliently in the expanding direction of the clamping jaws. With release of the catch, the clamping pliers thus always spring into their open position. Furthermore, a measure of even independent importance consists in the clamping force of the pliers being greater than the force which is necessary for release of the catch. This results in immediate release and opening of the clamping pliers without the catch-equipped pliers arm having to be gripped for the purpose. It is further provided for the catch to be acted upon by one arm of the expanding spring. The expanding spring thus has a double function; it functions as catch spring and as restoring spring for the clamping pliers. The corresponding accessibility in the direction of the catch is achieved by one arm of the expanding spring penetrating through a slot of the arcuate toothed strip. A further feature consists in the expanding spring being a rotary leg spring, the coil of which is secured by the scissors-articulation pin. Finally, it is also proposed for the ends of the clamping sections to provide bearing eyelets into which bearing pins of a bearing pocket of the clamping jaw project. The pockets are accessible so that such clamping jaws can be exchanged by means of an auxiliary tool, for example if specific gripping profiles are necessary. All that is required is for the clamping jaws to be exchanged. Finally, the situation where the clamping force is maintained by an elastic deformation of the clamping sections is also achieved. Powerful clamping, free from twisting, is present in the pivoting plane of the pliers arms.
An advantageous development of the clamping or expanding pliers according to the invention then consists in the catch and the actuating section being formed in two parts. This allows an intermediate function to be introduced. This is realized in that the spacing between the tooth-engagement point of the catch and toothing formation and the bearing pin for the rotatable mounting of the actuating section is shortened by a first actuation of the actuating section such that the two clamping sections are disengaged from the clamping position into a release position, the tooth engagement remaining maintained, said tooth engagement being released upon a second actuation of the actuating section. The second actuation thus no longer takes place counter to the clamping force of the tool. The first actuation requires a considerably reduced release force; the unblocking operation occurs in a xe2x80x9cmore gentlexe2x80x9d manner. It is provided here that, upon the first actuation, catch and actuating section are pivoted toward one another and are displaced. The displacement is made possible as a result of a longitudinal slot of the catch, the bearing pin engaging through said longitudinal slot. The further means are characterized here by a disengagement pin which is associated with the actuating section, engages in an angled slot of the catch and, in the position associated with the clamping position, engages in a first slot section, which runs substantially transversely to the connecting line between tooth-engagement point and bearing pin, and, in the position associated with the release position, passes into a second slot section, which runs substantially parallel to the connecting line. The toggle-joint-like control system achieved in this way operates in a positively controlled manner: first the disengagement, then parallel displacement of the disengagement pin in the last-mentioned, that is to say second, slot section. In this case, the second slot section runs in the same direction as the longitudinal slot. Catch and actuating section are acted upon by the same arm of the expanding spring. This acts in engagement-securing manner on the ratchet mechanism.